Method and System for Enhancing a Location Server Reference Database Through Round-Trip Time (RTT) Measurements

ABSTRACT

A mobile device in a cellular communication network collects round-trip time (RTT) measurements for a single active cell. The collected RTT measurements are transmitted to a location server. The location server uses the transmitted RTT measurements to calculate a GNSS position of the single active cell. One or more of the transmitted RTT measurements are taken by the mobile device, and/or are collected from other mobile devices in the single active cell. The transmitted RTT measurements are collected at different GNSS fixes in the same single active cell. The mobile device location stamps the collected RTT measurements using corresponding GNSS fixes, and transmits to the location server using a NML. The location server calculates the GNSS position of the single active cell using location stamped RTT measurements in the received NMLR to refine an associated reference database periodically or aperiodically.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This patent application is a continuation of U.S. patent applicationSer. No. 12/607,266, filed Oct. 28, 2009, which is incorporated hereinby reference in its entirety.

BACKGROUND OF TUE INVENTION

1. Field of the Invention

Certain embodiments of the invention relate to signal processing forcommunication systems. More specifically, certain embodiments of theinvention relate to a method and system for enhancing Location serverreference database through round-trip time (RTT) measurements.

2. Background of the Art

Location based services (LBS) are emerging as a value-added serviceprovided by a mobile communication network. LBS are mobile services inwhich the user location information is used in order to enable variousLBS applications such as, for example, enhanced 911 (E-911) services. Aposition of a mobile device is determined in different ways such as, forexample, using network-based technology, using terminal-basedtechnology, and/or hybrid technology (a combination of the formertechnologies). Many positioning technologies such as, for example, Cellof Origin (COO), Time of Arrival (TOA), Observed Time Difference ofArrival (OTDOA), Enhanced Observed Time Difference (E-OTD) as well asthe satellite-based systems such as the global positioning system (GPS),or Assisted-GPS (A-GPS), are in place to estimate the location of themobile device and convert it into a meaningful X, Y coordinate for LBSapplications.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for enhancing a location server referencedatabase through round-trip time (RTT) measurements, substantially asshown in and/or described in connection with at least one of thefigures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating an exemplary communication system thatis operable to enhance a reference database of a location server throughRTT measurements, in accordance with an embodiment of the invention.

FIG. 2 is a diagram illustrating an exemplary mobile device that isoperable to provide location stamped RTT measurements to a locationserver, in accordance with an embodiment of the invention.

FIG. 3 is a diagram illustrating an exemplary location server that isoperable to calculate cell GNSS fixes using corresponding locationstamped RTT measurements, in accordance with an embodiment of theinvention.

FIG. 4 is a flow chart illustrating an exemplary process utilized by alocation server to refine a reference database through location stampedRTT measurements, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor enhancing a location server reference database through round-triptime (RTT) measurements. In accordance with various exemplaryembodiments of the invention, a mobile device in a cellularcommunication network is operable to collect, for example, three or moreRTT measurements in a single active cell associated with the mobiledevice. A RTT measurement at a GNSS fix in the single active cell is thetransmission time between a data transmission from the GNSS fix to anassociated base station of the active cell and an acknowledgementreception at the GNSS fix from the associated base station of the activecell. The collected RTT measurements in the single active cell arecommunicated or transmitted to a location server. The location server isoperable to use the transmitted RTT measurements to calculate a GNSSposition of the single active cell. One or more of the transmitted RTTmeasurements may be taken by the mobile device, and/or may be collectedfrom one or more other mobile devices associated with the single activecell. The transmitted RTT measurements are collected at different GNSSfixes (longitude, latitude) in the same single active cell. The mobiledevice may be operable to location stamp the collected RTT measurementsusing corresponding GNSS fixes, and transmit to the location server, forexample, over a Network Management Layer (NML). The location server maybe operable to calculate the GNSS position of the single active cellusing RTT measurements and corresponding GNSS fixes, which are receivedover the NML. The calculated GNSS position of the single active cell maybe used to refine an associated reference database, which may be refinedor updated periodically or aperiodically.

FIG. 1 is a diagram illustrating an exemplary communication system thatis operable to enhance a reference database of a location server throughRTT measurements, in accordance with an embodiment of the invention.Referring to FIG. 1, there is shown a communication system 100. Thecommunication system 100 comprises cells 110 a-110 b, a location server120, a satellite reference network (SRN) 130 and a GNSS satelliteinfrastructure 140. The cell 110 a comprises a base station (BS) 101 aand a plurality of associated mobile devices, of which the GNSS enabledmobile devices 102-106 and a mobile device 108 are illustrated. The cell110 b comprises a BS 101 b and a plurality of associated mobile devices,of which GNSS enabled mobile devices 112-116 and a mobile device 118 areillustrated. The GNSS satellite infrastructure 140 comprises a pluralityof visible GNSS satellites, of which GNSS satellites 140 a-140 c aredisplayed.

The cells 110 a-110 b comprises geographical areas covered by the BS 101a and the BS 101 b, respectively. Each cell may be identified by aunique cell identifier (Cell-ID). For each mobile device such as theGNSS enabled mobile device 102 in the communication system 100, a cellsuch as the cell 101 a may be associated with an active cell set, acandidate cell set or a neighbor cell set of the GNSS enabled mobiledevice 102. The active cell set comprises a list of cells that arecurrently connected to the GNSS enabled mobile device 102. The candidatecell set comprises a list of cells that are not currently connected tothe GNSS enabled mobile device 102, but with associated pilot orreference signals strong enough to be added to the active cell set. Theneighbor cell set comprises a list of cells that are continuouslymeasured by the GNSS enabled mobile device 102 and corresponding pilotor reference signals are not strong enough to be added to the activecell set.

A mobile device such as the GNSS enabled mobile device 102 may comprisesuitable logic, circuitry and/or code that may be operable tocommunicate with a wireless communication network such as a WCDMAnetwork via the BS 101 a. The GNSS enabled mobile device 102 may beoperable to communicate radio signals that are compatible with varioustelecommunication standards such as, for example, 3GPP, with the BS 110a. With GNSS enabled, the GNSS enabled mobile device 102 may be operableto receive GNSS signals from a plurality of visible GNSS satellites suchas the GNSS satellites 140 a through 140 c. The received GNSS signalsmay be utilized to determine a GNSS fix associated with the GNSS enabledmobile device 102. A quick GNSS fix of the GNSS enabled mobile device102 may be determined using reference position information, which may beprovided by the location server 120. In this regard, the GNSS enabledmobile device 102 may be operable to select one or more cells from theassociated active cell set. For each selected cell such as the cell 101b, the GNSS enabled mobile device 102 may be operable to take or collectRound Trip Time (RTT) measurements at, for example, three or moredifferent GNSS fixes in the cell 101 b. A RTT measurement at a GNSS fixin an active cell is the transmission time between a data transmissionfrom the GNSS fix to the active cell and an acknowledgement reception atthe GNSS fix from the active cell. A RTT measurement at a GNSS fix in anactive cell may be directly related to a distance between the GNSS fixand an associated BS of the active cell. The collected RTT measurementsat different GNSS fixes in the cell 101 b may be location stamped usingcorresponding GNSS fixes. In an exemplary embodiment of the invention,three or more location stamped RTT measurements may be collected. Thecollected location stamped RTT measurements may be measured by the GNSSenabled mobile device 102 alone or may be collected from other mobiledevices such as the GNSS enabled mobile device 104 associated with thesame active cell. The GNSS enabled mobile device 102 may be operable tosend the collected location stamped RTT measurements via a serving BSsuch as the BS 101 a over a NML to the location server 120. Thecollected location stamped RTT measurements may be utilized foraccurately positioning the corresponding active cell such as the cell110 b.

The location server 120 may comprise suitable logic, circuitry and/orcode that may be operable to access the satellite reference network(SRN) 130 to collect GNSS satellite data by tracking GNSS constellationsthrough the SRN 130. The location server 120 may be operable to utilizethe collected GNSS satellite data to build a reference database, whichmay be utilized to provide GNSS assistance data to support LBS services.In this regard, the location server 120 may be operable to receive NMLsfrom a plurality of associated mobile devices. The received NMLs maycomprise location stamped RTT measurements. The location server 120 maybe operable to utilize the received location stamped RTT measurements tocompute GNSS positions of one or more cells of interest. In an exemplaryembodiment of the invention, three or more location stamped RTTmeasurements in a particular cell may be required to calculate acorresponding GNSS position of the particular cell. Associated GNSSfixes of the location stamped RTT measurements are different GNSSpositions in the particular cell. The location server 120 may beoperable to utilize the calculated GNSS positions of corresponding cellsof interest to refine or update reference database. The location server120 may be operable to message in exemplary formats compatible withtelecommunication networks such as WCDMA. For example, the locationserver 120 may be WCDMA standard compliant by supporting messaging inRRLP format, PCAP interface and/or OMA SUPLv1.0. The location server 120may be configured to communicate with a mobile device such as the GNSSenabled mobile device 102 in either a user-plane or a control-plane.

The SRN 130 may comprise suitable logic, circuitry and/or code that maybe operable to collect and distribute data for GNSS satellites on acontinuous basis. The SRN 130 may comprise a plurality of GNSS referencetracking stations located around the world to provide A-GNSS coverageall the time in both a home network and/or any visited network. Thisallows users of the GNSS enabled devices such as the GNSS enabled mobiledevice 102 to roam with associated LBS anywhere in the world. The SRN130 may be operable to ensure high levels of availability andreliability for LBS performance.

The GNSS satellites 140 a through 140 c may comprise suitable logic,circuitry and/or code that may be operable to generate and broadcastsatellite navigational information in suitable radio-frequency (RF)signals to various GNSS capable devices such as, the GNSS enabled device102. The broadcast satellite navigational information may be utilized tosupport LBS services. The GNSS satellites 140 a through 140 c may beGPS, Galilee, and/or GLONASS satellites.

In an exemplary operation, a mobile device such as the GNSS enabledmobile device 102 may be operable to select a cell from an associatedactive cell set. The GNSS enabled mobile device 102 may be operable totake or collect RT measurements at, for example, three or more differentGNSS fixes in the selected cell. The collected RTT measurements may belocation stamped using the corresponding GNSS fixes, where the RTTmeasurements are performed. The GNSS enabled mobile device 102 may beoperable to communicate with an associated serving BS such as the BS 101a to send the location stamped RTT measurements over a NML to thelocation server 120. The location server 120 may be operable to utilizethe location stamped RTT measurements in the received NML to compute theGNSS position of the cell 110 b. The location server 120 may be operableto utilize the computed GNSS position of the cell 110 b to refinereference database.

FIG. 2 is a diagram illustrating an exemplary mobile device that isoperable to provide location stamped RTT measurements to a locationserver, in accordance with an embodiment of the invention. Referring toFIG. 2, there is shown a GNSS enabled mobile device 200 comprising aprocessor 202, a cellular radio 204, a GNSS radio 205 and a memory 206.

The processor 202 may comprise suitable logic, circuitry, interfacesand/or code that may be operable to manage and/or control operations ofassociated component units such as, for example, the cellular radio 204and the GNSS radio 205. For example, the processor 202 may be operableto activate the cellular radio 204 to take or collect RTT measurementsat three or more different GNSS fixes in a cell of interest. The cell ofinterest may be selected from an associated active cell set of themobile device 200. The collected RTT measurements may be taken by thecellular radio 204 or may be collected from other mobile devices thatare associated with the cell of interest. The processor 202 may beoperable to transmit the location stamped RTT measurement of the cell ofinterest to the location server 120 via a serving BS such as the BS 101a. The transmitted location stamped RTT measurements may be utilized forcomputing the GNSS position of the cell of interest.

The cellular radio 204 may comprise suitable logic, circuitry,interfaces and/or code that may be operable to transmit and/or receiveradio signals in cellular spectrum. The radio signals transmitted and/orreceived may be processed via the processor 202. In this regard, thecellular radio 204 may be operable to perform RTT measurements atparticular GNSS fixes within an active cell of interest. The RTTmeasurements may be location stamped and transmitted over a NML to thelocation server 120.

The GNSS radio 205 may comprise suitable logic, circuitry, interfacesand/or code that may be operable to receive GNSS satellite broadcastsignals. The received GNSS satellite broadcast signals may be processedto provide a navigation solution such as a GNSS fix of the mobile device200. In this regard, RTT measurements may be performed or collected forthree or more different GNSS fixes within an active cell of interest.The resulting RTT measurements may be location stamped usingcorresponding GNSS fixes and communicated to the location server 120 forcell positioning.

The memory 206 may comprise suitable logic, circuitry, interfaces and/orcode that may be operable to store information such as executableinstructions and data that may be utilized by the processor 202 and/orother associated component units such as, for example, the cellularradio 204. The memory 206 may comprise RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage.

In an exemplary operation, the mobile device 200 may be operable toreceive broadcast satellite signals via the GNSS radio 205. The receivedsatellite signals may be used to calculate a navigational solution suchas a GNSS fix of the mobile device 200. For a particular GNSS fix, theprocessor 202 may be operable to activate the cellular radio 204 to takeor collect RTT measurements for an active cell of interest. The RTTmeasurements may be taken by the cellular radio 204 or may be collectedfrom other mobile devices that are associated with the active cell ofinterest. The RTT measurements may be generated from, for example, threeor more different GNSS positions in the same active cell of interest.The RTT measurements may be location stamped using corresponding GNSSfixes. The location stamped RTT measurements may be transmitted over aNML to the location server 120. The transmitted location stamped RTTmeasurements may be utilized to enhance cell positioning.

FIG. 3 is a diagram illustrating an exemplary location server that isoperable to calculate cell GNSS fixes using corresponding locationstamped RTT measurements, in accordance with an embodiment of theinvention. Referring to FIG. 3, there is shown a location server 300.The location server 300 comprises a processor 302, a reference database304 and a memory 306.

The processor 302 may comprise suitable logic, circuitry, interfacesand/or code that may be operable to access the SRN 130 to collect GNSSsatellite data by tracking GNSS constellations through the SRN 130. Theprocessor 302 may be operable to utilize the collected GNSS satellitedata to build the reference database 304, which may provide GNSSassistance data to support LBS services. In this regard, the processor302 may be operable to receive NMLs from a plurality of mobile devicesvia a communication network such as a WCDMA network. The received NMLsmay comprise location stamped RTT measurements, which comprise RTTmeasurements and corresponding GNSS fixes where the RTT measurements areperformed.

The processor 302 may be operable to utilize the received locationstamped RTT measurements to compute GNSS locations of one or moreassociated cells of interest. For example, for a particular cell, theprocessor 302 may be operable to extract location stamped RTTmeasurements corresponding to the particular cell from the receivedNMLs. The extracted location stamped RTT measurements comprise RTTmeasurements and corresponding GNSS fixes in the particular cell. Anextracted location stamped RTT measurement is directly related to adistance between an associated GNSS fix and the particular cell, forexample, in steps of 50 m as per the following series of {25, 75, 125,175, 225, 275, 325, 375, 425, 475}. In an exemplary embodiment of theinvention, three or more location stamped RTT measurements in the sameparticular cell may be required so as to compute the GLASS location ofthe particular cell.

The processor 302 may be operable to approximate the distance betweentwo points on the surface of the earth using a corresponding distance ina flat surface. In this regard, in instances where parameter Loc_Cell isthe location of a cell of interest and parameter GNSS_RTT is a GNSS fixwhere the corresponding RTT measurement is performed, the distancebetween the GNSS fix of the corresponding RTT measurement (GNSS_RTT) andthe location of the cell of interest (Loc_Cell), namely,Distance_Cell_RTT, may be approximated utilizing the followingrelationship:

Distance_(—) BSS _(—) RTT=|GNSS _(—) RTT−Loc _(—) BS|

that is a corresponding distance in a flat surface. The parameterDistance_Cell_RTT is directly related to a corresponding RTT measurementin steps of 50 m. The location of the cell of interest may be calculatedor solved using the following exemplary relationship:

${GNSS\_ BS} = {\min {\sum\limits_{i > 2}{{{{Distance\_ BS}{\_ RTT}{\_ i}} - {{{{GNSS\_ RTT}{\_ i}} - {Loc\_ BS}}}}}}}$

where i is an integer and is greater than 2. The calculated location ofthe cell of interest may be utilized to refine the reference database304. The processor 302 may be operable to communicate message inexemplary formats that are compatible with telecommunication networkssuch as WCDMA. For example, the processor 302 may be operable to supportmessaging in RRLP format, PCAP interface and/or OMA SUPLv1.0. Theprocessor 302 may be configured to communicate with a mobile device suchas the GNSS enabled mobile device 102 in either a user-plane or acontrol-plane for a NML periodically or aperiodically.

The reference database 304 may comprise suitable logic, circuitry,interfaces and/or code that may be operable to manage and/or store datacomprising reference positions and/or location information that iscaptured, determined and/or learned from a plurality of associatedmobile devices. In this regard, the reference database 304 may berefined or updated using cell GNSS locations that are derived orcalculated using corresponding location stamped RTT measurements. Thecontents in the reference database 304 may be updated as needed orperiodically.

The memory 306 may comprise suitable logic, circuitry, interfaces and/orcode that may be operable to store information comprising executableinstructions that may be utilized by the processor 302. The executableinstructions may comprise algorithms that may be utilized to calculateGNSS locations of one or more cells of interest according tocorresponding location stamped RTT measurements. The memory 306 maycomprise RAM, ROM, low latency nonvolatile memory such as flash memoryand/or other suitable electronic data storage.

In operation, the processor 302 may be operable to learn and refinelocation information for one or more cell of interest according tocorresponding location stamped RTT measurements. The processor 302 maybe operable to receive NMLs from a plurality of associated mobiledevices such as, the GNSS enabled mobile device 102. The received NMLsmay comprise location stamped RTT measurements. A location stamped RTTmeasurement comprises a RTT measurement and an association GNSS fixwhere the RTT measurement is performed. GNSS locations of one or moreassociated cells of interest may be calculated using the receivedlocation stamped RTT measurements. In various exemplary embodiments ofthe invention, three or more location stamped RTT measurements that aretaken at different GNSS fixes in a cell of interest may be required tocompute a corresponding location of the cell of interest. The calculatedcell GNSS locations may be utilized to refine the reference database 304to enhance LBS service performance such as speed and/or accuracy. Thereference database 304 may be updated periodically or on an as neededbasis.

FIG. 4 is a flow chart illustrating an exemplary process utilized by alocation server to refine a reference database through location stampedRTT measurements, in accordance with an embodiment of the invention.Referring to FIG. 4, the exemplary steps start with step 402, where amobile device such as the mobile device 200 may be operable to select acell of interest from an associated active cell set. In step 404, themobile device 200 may be operable to take or collect from other mobiledevice RTT measurements at, for example, three or more different GNSSpositions in the selected cell of interest. In step 406, the mobiledevice 200 may be operable to location stamp the collected RTTmeasurements with corresponding GNSS fixes. In step 408, the mobiledevice 200 may be operable to upload the location stamped RTTmeasurements over a NML to the location server 300. In step 410, thelocation server 300 may be operable to calculate a GNSS location of theselected cell using the RTT measurements and corresponding GNSSpositions received over a NML. In step 412, the location server 300 maybe operable to utilize the calculated GNSS location of the selected cellto update the reference database 304. The exemplary steps may be endedin step 414.

In step 416, it may be determined whether the RTT measurement processmay continue for next active cell. In instances where the RTTmeasurement process may continue for the next active cell, the exemplarysteps may return to step 402.

In step 416, in instances where the RTT measurement process may notcontinue for the next active cell, the exemplary steps may end at step414.

Aspects of a method and system for enhancing a location server referencedatabase through RTT measurements are provided. In accordance withvarious exemplary embodiments of the invention, as described withrespect to FIG. 1 through FIG. 4, a mobile communication device such asthe mobile device 200 may be operable to collect, for example, three ormore RTT measurements in a single active cell such as the cell 110 bassociated with the mobile device 200. The collected RTT measurements inthe single active cell may be transmitted to the location server 300.The location server 300 may be operable to use the transmitted RTTmeasurements to calculate a GNSS position as a position estimate of theactive cell. For example, the location server 300 may be operable toapply various algorithms such as, for example, server-basedtriangulation algorithms to calculate the position estimate of theactive cell using the received RTT measurement transmissions. One ormore of the transmitted RTT measurements may be taken by the mobiledevice 200, and/or may be collected from one or more other mobiledevices in the single active cell. The transmitted RTT measurements arecollected at different GNSS fixes in the same single active cell. Thecollected RTT measurements may be location stamped using correspondingGNSS fixes. The mobile device 200 may be operable to transmit thelocation stamped RTT measurements to the location server 300, forexample, using a NML. The location server 300 may be operable tocalculate the GNSS position of the single active cell using RTTmeasurements and corresponding GNSS fixes in the received NML. Thecalculated GNSS position of the single active cell may be used to refinethe reference database 304. The reference database 304 may be refined orupdated periodically or aperiodically.

Another embodiment of the invention may provide a machine and/orcomputer readable storage and/or medium, having stored thereon, amachine code and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for a methodand system for enhancing a location server reference database throughRTT measurements.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method of processing signals, the method comprising: performing bya mobile communication device: collecting round trip time (RTT)measurements for an active cell associated with the mobile communicationdevice; and transmitting the collected RTT measurements to a locationserver, wherein the RTT measurements collected for the active cell areused by the location server to calculate a GNSS location of the activecell.
 2. The method according to claim 1, wherein the step of collectingcomprises: collecting three or more RTT measurements taken by one ormore other mobile communication devices in the active cell.
 3. Themethod according to claim 2, wherein the step of collecting the three ormore RTT measurements comprises: collecting the one or more of the threeor more RTT measurements from the one or more other mobile devicesassociated with the active cell.
 4. The method according to claim 1,wherein the step of collecting comprises: collecting each of the RTTmeasurements at a different GNSS fix in the active cell.
 5. The methodaccording to claim 4, further comprising: location stamping each of thecollected RTT measurements using a corresponding GNSS fix in the activecell associated with the mobile communication device.
 6. The methodaccording to claim 5, further comprising: transmitting the locationstamped RTT measurements to the location server.
 7. The method accordingto claim 1, further comprising: selecting the active cell from a set ofactive cells associated with the mobile communication device.
 8. Amobile communication device, comprising: a cellular radio moduleconfigured to collect round trip time (RTT) measurements for an activecell associated with the mobile communication device, wherein the RTTmeasurements comprise RTT measurements for one or more other mobiledevices; and a processor configured to direct the cellular radio moduleto collect the RTT measurements and transmit the collected RTTmeasurements to a location server for use in calculating a GNSS locationof the active cell.
 9. The mobile communication device of claim 8,further comprising: a GNSS radio module configured to receive GNSSsatellite broadcast signals and calculate a GNSS fix of the mobilecommunication device corresponding to one of the RTT measurements. 10.The mobile communication device of claim 9, wherein the processor isfurther configured to location stamp each of the RTT measurements usingthe corresponding GNSS fix and transmit the location stamped RTTmeasurements to the location server.
 11. The mobile communication deviceof claim 9, wherein the processor is further configured to direct theGNSS radio module to collect each of the RTT measurements at a differentGNSS fix in the associated active cell.
 12. The mobile communicationdevice of claim 8, wherein the RTT measurements comprise three or moreRTT measurements.
 13. The mobile communication device of claim 12,wherein the processor is further configured to direct the cellular radiomodule collect at least one of the three or more RTT measurements fromat least one other mobile communication device in the active cell. 14.The mobile communication device of claim 12, wherein the processor isfurther configured to direct the cellular radio module to collect the atleast one of the three or more RTT measurements from the at least oneother mobile communication device associated with the active cell.
 15. Amethod comprising: receiving at a location server round trip time (RTT)measurements collected by at least one mobile communication device foran active cell associated with the mobile communication device;calculating at the location server a GNSS position of the active cellusing the received RTT measurements; and updating location informationfor the active cell in an associated reference database using thecalculated GNSS position of the active cell.
 16. The method of claim 15,wherein the step of updating further comprises refining the referencedatabase associated with the location server.
 17. The method of claim15, wherein the step of receiving further comprises receiving three ormore RTT measurements from the at least one mobile communication device.18. The method of claim 15, wherein the step of receiving furthercomprises receiving location stamped RTT measurements from the at leastone mobile communication device.
 19. The method of claim 18, wherein thestep of receiving further comprises receiving the location stamped RTTmeasurements from the at least one mobile communication device in theactive cell.
 20. The method of claim 18, wherein the step of receivingfurther comprises receiving the location stamped RTT measurements fromthe at least one mobile communication device associated with the activecell.